fs: honor flush option in writeFileSync utf8 fast path#63887
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fs: honor flush option in writeFileSync utf8 fast path#63887MarshallOfSound wants to merge 1 commit into
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The C++ utf8 fast path added in 4466dee does not perform an fsync, but the gate routing writeFileSync through it did not consult the flush option added in e01c1d7. As a result writeFileSync(path, data, { encoding: 'utf8', flush: true }) wrote without flushing, while the same call without an explicit encoding flushed correctly. Skip the fast path when flush is requested. appendFileSync delegates to writeFileSync and was affected the same way. Extend the existing flush tests with the explicit-utf8-encoding case for both; the new cases fail without this change. Signed-off-by: Sam Attard <sattard@anthropic.com>
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Description of Change
fs.writeFileSync(path, data, { encoding: 'utf8', flush: true })does not fsync. The C++ utf8 fast path (4466dee) skips the JS write loop that performs the flush, and its gate never checked theflushoption (e01c1d7, which predates it). The same call without an explicit encoding misses the fast path and flushes correctly. Verified with strace: zerofsyncsyscalls on the fast path, one on the slow path.This PR skips the fast path when
flush: trueis set, routing those writes through the existing open/write/fsync/close path.appendFileSyncdelegates towriteFileSyncand is fixed by the same change.Affects every release line since v21.3.0.
Extended the existing flush tests (
test-fs-write-file-flush.js,test-fs-append-file-flush.js) with the explicit-utf8-encoding case — the only combination that takes the fast path, and exactly the cell their matrices didn't cover. Both new cases fail without this change.Checklist
test/parallel/test-fs-*pass